Help this Newfag™ get started with PnP

[FritzedProcess]

FATE is also a system that just uses D6. It's a generic system -a spinoff of FUDGE, actually- so you can adapt it to any setting (and there's plenty of published settings for FATE; any setting being released for 3rd-party systems these days is sure to get a FATE adaptation). I'm not a big fan of this system, but it's there, it's not complicated and you don't need any fancy die.

There's also the old West End Games Star Wars which also relies solely on D6, which has already been mentioned here. It's a beginner-friendly system and I'd recommend it, if you can find it as it's been out of print for a while.

Shadowrun uses D6 only also, and it's currently in its 5th edition. While the rules have improved vastly from the days of 2nd and 3rd edition and they are much simpler, they are still rather complicated at times and character generation can take 2-3 hours easily. Magic and hacking have their own separate subsystems which can be cumbersome for a first-time GM. Also, Catalyst Games (the publisher) has been nickel and diming a lot with the supplements in this edition, and most of those are rehashed (and sometimes split) 4th edition supplements, of which the Almanac and Attitude are still the best ever published. It's one of the very few cyberpunk games out there that only uses D6 (there's also Interface Zero 2.0 for FATE, IIRC)

There's also Degenesis, a German post-apocalyptic RPG that's been translated into English and also uses D6. The system is very elegant and uncomplicated, and the setting is quite interesting but it requires a fair bit of reading (the game in print comes in two hefty tomes, about 350 pages each), so it's not for every group (it's still more accessible for most groups than, say, Eclipse Phase, but this might sound like Greek to you at this point as it's a rather niche game).

 

[Xorphitus]

I like Shadowrun but it is one of those systems that is a bit more complex since it has plenty of rules. The 5th edition core is almost 500 pages so if you plan on game mastering you better have a bunch of extra time to get a grasp of those rules and setting background. Easily can spend an entire evening trying to get characters made for that game.

 

[FritzedProcess]

There's also "In Nomine", by Steve Jackson Games, which uses rolls of d666 (which is actually 3d6). It's an adaptation of the vastly superior "In Nomine Satanis/Magna Veritas", a French roleplaying game. Why superior, you may be wondering? Well, the system's pretty much the same in both, but the French version is quite humorous and grotesque, whereas the US version was watered down to make it more "palatable", and I guess the "Satanis" was pulled from the title to avoid getting in trouble. Alas, the only way you'll get to enjoy the original game is if you can read French, Spanish or German, as the game was never actually translated into English (the Steve Jackson one is based on it, not an actual translation), and Spanish and German versions are hard to come by, as they were printed in the early 90s. Otherwise, you may want to look into the Steve Jackson game, but better games have been recommended in this thread, TBH.

The system's rather broken, by the way - forget about game balance when playing this.

 

[Lord Rocket]

OK OP here is some real serious advice for you: play a dungeon fantasy game like D&D. It doesn't matter what system you use, just that it's in a dungeon and the characters are exploring it. Why? Because unless you manage to horn in on that one dude's Pathfinder game, YOU are going to be the DM and dungeon fantasy is the easiest genre to DM by a considerable margin.

Here is the difference between DMing a DungFan game versus, say, a Call of Cthulhu sesh:

CoC : create the environment. Create the NPCs. Anticipate what the players will do and provide additional detail to those areas. Make sure the puzzles are not so difficult that they can't solve them (eventually); create enough clues so that the players will get at least some of them. Create back-up plans so you can railroad the PCs if necessary; you will probably need to work to keep the game on track as players will often misidentify what is important. Have a high verbal IQ so you can spook them with creepy words and shit. Adventures must be designed tightly as they are fundamentally linear (clue a leads to cult b etc.) -- balance matters. DMs most important skill: storytelling.
DF : create the environment. Maybe make some NPCs if you can be bothered. Once this is done, get yourself some reaction rules for the monsters and the game practically plays itself; the PCs will drive the game by exploring the dungeon and choosing what is relevant with very little input from your own bad self. Anything that is too obtuse, the players can ignore or return to at any point. Undiscovered content can be easily reused later (because most of it is based on the environment, not the story, it is very 'modular' like that). Quite often the players will, in an attempt to rationalise something bizarre on your behalf, will come up with cool ideas that you can steal. Strict balance is unnecessary because all (non-random) encounters are optional, unless you made the dungeon really linear, which you shouldn't have. DMs most important skill: being impartial.

ie. exploration puts the onus on players to drive the game and also makes it very clear, to them, what they should be doing. And they'll do a lot of the work for you. You can always have them find a treasure map if they're not sure where to go next or if they think they need a proper goal.

Additionally, there is a lot of mechanical support for dungeon fantasy, by which I mean tools that will generate content for you (both dice and computer based). Random generators are a fucking godsend, since they are great for inspiring new ideas of your own. Here's a sampling:
http://d-infinity.net/digital-dice/random-tavern-generator
http://www.mithrilandmages.com/utilities/LLTreasure.php
http://inkwellideas.com/2011/09/isocahedral-worldmap-generator/
http://www.dizzydragon.net/adventuregenerator/gen
http://angband.oook.cz/steamband/Tricks.pdf
http://angband.oook.cz/steamband/Treasure.pdf
edit: http://www.mithrilandmages.com/utilities/LLOubliette.php

Many retroclones (rip offs loving recreations of early eds. of D&D: https://en.wikipedia.org/wiki/Dungeons_&_Dragons_retro-clones) feature dice & paper based dungeon generators (on that page: OSRIC and Labyrinth Lord at least definitely do. Off of it, Hulks and Horrors has a goofy sci-fi environment generator).
(Personally I just throw dice at a page and draw rooms around wherever they land; the number on the dice indicates how many doors are in that room, then I draw corridors between the rooms based on that. Doors that ultimately lead nowhere indicate secrets of some sort. Then I roll to see if there's monsters etc. in there too).

TLDR: making a dungeon using random tables and then letting the players walk around it while you jerk off under the table is way easier than any other kind of DMing, so just do that.

Alright even though I said it doesn't matter I'm going to suggest you suck it up and buy some cheap dice sets on eBay or make some spinners (these things: https://mrstsfirstgradeclass-jill.blogspot.com.au/2011/07/roll-spelling-word.html) so you can play TSR-era D&D or a retroclone, because it's the ruleset that interacts best with dungeon crawling... although you could easily lift the D&D exploration rules and put them in another game if you wanted.
It's less combat-focussed than WotC editions because most of your XP will come from treasure, not killing stuff, making it economical to burgle monsters rather than kill, rape and plunder them. It also lacks a skill system -- when you're more experienced you'll notice that players tend to stare at their character sheets when trying to solve problems in skill based games, because what they can do is constrained by the numbers thereon. Meanwhile they'll come up with all sorts of whacky shit without one, so long as you're willing to let their 'cunning' plans succeed.* Also, better interactions with traps as opposed to rolling Detect Trap, roll Disarm Trap ad nauseum. Related recommendation: no Thieves.

* Skill systems are useful when you have a bad GM, ie. one that gainsays players all the time, because that way the dice rolls allow players to have at least some agency. They're really not necessary when the GM encourages player stupidity creativity.

 

[Wayward Son]

As nikolokolus has said, Sword and Wizardry is a fun and relatively simple system in the vein of DnD. It's actually how I introduced a couple of my friends to PnP. Also, most will disagree with me, but I found the majority of 2e DnD simple and easy to understand when I began playing with an experienced player. Also, any Infinity Engine game is a RTwP conversion of 2e, and follows them pretty faithfully from what I've seen, so you can get the basic handle on the rules from there. Might be good to start there if you think your English is good enough and you can afford it.